﻿/*
   Created 2009 December 4, Randall Maas
   Copyright (c) 2009, Randall Maas
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

   Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

   Neither the name of Blackwood Designs, LLC nor the names of its contributors
   may be used to endorse or promote products derived from this software without
   specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   THE POSSIBILITY OF SUCH DAMAGE.
*/

using System;
using System . Collections . Generic;
using System . Runtime . InteropServices;
using System . Runtime . InteropServices . ComTypes;

/// <summary>
/// Helpers to access COM items
/// </summary>
static partial class COM
{
   /// <summary>
   /// Creates an object that is an instance of the type (as identified by its Guid)
   /// </summary>
   /// <param name="G">The Guid of the type</param>
   /// <returns>null on error, otherwise the object.  This object must be
   /// released later with Marshal . ReleaseComObject()</returns>
   internal static object CreateInstanceFromType(Guid G)
   {
      Type T = Type . GetTypeFromCLSID(G);
      if (null == T)
        return null;
      return Activator . CreateInstance(T);
      // I don't think we need to Marshal . ReleaseComObject(T);
   }


   /// <summary>
   /// Enumerates all of the monikers
   /// </summary>
   /// <param name="EnumMoniker">The moniker enumerator to enumerator over</param>
   /// <returns>The Enumerator</returns>
   /// <remarks>The caller must Marshal . AddRef() the item if it wishes to
   /// access the moniker after the iteraiton.  The Next() will release the object</remarks>
   static internal IEnumerable<IMoniker> Enumerator(IEnumMoniker EnumMoniker)
   {
      IMoniker[] mon = new IMoniker[1];
      IntPtr result =  Marshal.AllocHGlobal(8);
      mon[0] = null;
      while (  0 == EnumMoniker . Next(1, mon,  result)
            && null != mon[0])
      {
         yield return mon[0];
         Marshal . ReleaseComObject(mon[0]);
         mon[0] = null;
      }
      Marshal . FreeHGlobal(result);
   }

}
